Blower Impeller with Segmented Blade Tips for Noise Attenuation
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Solution Overview
Problem
Blower assemblies with backward curved impellers generate undesirable tonal noises due to air pressure pulses caused by blade pass tones, particularly when blade tips approach the cutoff point, leading to objectionable noise and reduced efficiency.
Innovation Solution
The design includes an impeller with backward curved blades featuring a tip portion with a transition point that divides the radially outer edge into two portions, creating a constant-width first radial gap and a larger second radial gap between the cutoff point and the blade tips, which reduces pressure pulses and noise by positioning the second portion further away from the cutoff point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the clearance between the backward curved impeller blade tips and the cutoff point is decreased to increase blower assembly performance, then productivity is improved, but object-generated harmful factors worsen due to generation of air pressure pulses that produce undesirable tonal noises
Solution Approach 1:
The blade tip is segmented into two distinct portions: a first portion that extends closely to the cutoff point to maintain performance, and a second portion that is positioned further away to reduce noise. This segmentation allows each portion to serve different functions - the first portion maintains airflow efficiency while the second portion minimizes pressure pulse generation
Solution Approach 2:
Different sections of the blade tip are given different spatial characteristics. The first portion has a geometry optimized for performance (close to cutoff point) while the second portion has a geometry optimized for noise reduction (further from cutoff point). This local differentiation resolves the contradiction by allowing performance-critical areas to maintain close clearance while noise-critical areas maintain larger clearance
2Productivity
If the blade edges are positioned close to the housing inlet edge to improve performance, then productivity is improved, but object-generated harmful factors worsen due to additional pressure pulses causing undesirable tonal noise
Solution Approach 1:
The blade structure is segmented such that the main blade body can be positioned close to the housing inlet for performance, while the blade tip portions (especially the second portion) are positioned away from the cutoff point to reduce noise. This segmentation allows independent optimization of performance and noise characteristics
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively attenuates blade pass tones and pressure pulses, maintaining blower assembly performance while minimizing undesirable noise, thus enhancing user experience and operational efficiency.
Implementation Method 1
when blade tips pass within close proximity to the cutoff point, they generate air pressure pulses that produce undesirable tonal noises known as blade pass pure tones
Data Source
AI summary
A blower assembly includes a housing including an outlet and a cutoff point positioned proximate the outlet. The blower assembly also includes an impeller including a plurality of blades that each includes a tip portion including a radially outer edge and a transition point that divides the radially outer edge into a first portion and a second portion. The impeller is positioned within the housing such that a first radial gap is defined between the cutoff point and the first portion and a second radial gap is defined between the cutoff point and the second portion. The first radial gap includes a constant width that is shorter than a width of the second radial gap.